High-frequency electron discharge tube



Dec. 19, 1950 "M. J. o, STRUTT ETAL HIGH-FREQUENCY ELECTRON DISCHARGE TUBE Filed July 12, 1946 ///I Ill/l l/l/l/l/l/l/ 'INVENTORS. WWW/w 0170mm? BY ALBEIPZ'WMZZEL Patented Dec. 19, 1950 UNITED STATES HIGH-FREQUENCY ELECTRUN DISCHARGE TUBE Maximilia'an Julius Gtto Strutt, Aldert van der Ziel, and Kornelis Swier Knol, Eindhoven, Netherlzinds, assignor's to Hartford National Bank and Trust Company, Hartford, 001111., as

trustee Application July 12, 1946, Serial No. 682,983 inv the Netherlands March 1, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 1, 1963 l Claims.

of the size of the discharge tubes utilised. In

order tobe able to transmit or produce oscillation having such a small wavelength, the discharge tubes have been given smaller and smaller dimensions. Owing ot this reduction; more particularly owing to the reduction of the cathode area, the power to be given oii by'the discharge tube decreases so strongly that any production or transmission of energy at the said very high frequencies no longer takes place.

Now, the present invention provides means whereby electrical osillations of very high frequency are transmitted or produced with the aid of a discharge tube whose size must not necess'arily' be small relatively to the wavelength of the oscillations; the electrodes of this tube, more particularly the cathode, as compared with the electrodes of the discharge tubes utilised before, can even be very large so that it is on principle possible to transmit or to produce oscillations with any desired power.-

According to the invention, the production or transmission of oscillations is effected with the use of a discharge tube having an electrode system shaped in the form of one or more hollow wave-guides the dimension of which is a direction normal to the direction of propagation of the oscillations in the hollow wave-guides and normal to the direction of the electronic current in the tube is larger than half of the wavelength which the said oscillations exhibit when propagating in the free space. Accordingly, the elec trodes either form part of the hollow wave-guides or constitute as a whole the boundary thereof. If' the electrode system is constituted by one or more closed hollow wave-guides, the electrode system measured in the direction of propagation of the oscillations is preferably given a length smaller than half of the wavelength which the said oscillations exhibit when propagating inside these hollow wave-guides.

If, on the contrary, the electrode system is constituted by one or more non-closed hollow wave-guides, then the electrode system measured in the direction of propagation of the oscillations is preferably given a length smaller than a quarter of the wavelength which the said oscillations exhibit with propagation inside these hollow wave-guides.

. A highly satisfactory operation is obtained if the oscillations to be transmitted or produced are of the so-called Ho-type, that is oscillations of which the electric strength E does not comprise a component in the direction of propagation. Further, it is frequently desirable to ensure that the direction of the electric strength is the same as that of the electronic current in the discharge tube.

Circuits have previously been suggested in which electrical oscillations are transmitted. with the aid of discharge tubes arranged inside the hollow wave-guides. In these known circuits, however, the electrode systems of. the discharge tubes do not have the shape of hollow wave- 7 guides so that the advantage ofiered by the present invention are not obtained.

In order that the invention may be more clearly understood and readily carried into" effect it will be described more fully by reference to the accompanying drawing.

Fig. 1 is a perspective view of a preferred embodiment of an electron discharge tube, including rectangular waveguides, in accordance with the'invention,

Figs. 2 and 2a are schematic and structural showings respectively of a longitudinal cross section in the tube shown in Fig. 1, the ends of the WaVeguides in this instance being enclosed,

Figs. 3 and 3a are schematic and structural showings respectively of a longitudinal cross section of the tube in Fig. l, the ends of the waveguides in the instance being open,

Fig. 4 is a perspective view of a second discharge tube in accordance with the invention,

Fig. 5 is a longitudinal cross section of the tube shown in Fig. 4,

Fig.6 is a transverse section of the tube shown in- Fig. 1, and

Fig. '7 is a transverse cross section of. the tube shown in Fig. 4.

Figure 1 shows diagrammatically an amplifying circuit according to the invention in which the discharge tube used is a triode. The oscilla tions to be amplified are supplied to a triode- 2 through a Lecher line I, the amplified oscillations being derived from this tube with the aid of a Lecher line 3. The triode contains an electrode system which is constituted by an anode i, a control grid 5 and a cathode 6 and shaped in the form of two hollow waveguides the upper one of which is bounded by'anode i and control grid and the lower one by control grid 5 and cathode 6. The closure of the hollow waveguides at the front and at the sides will be dis cussed later in the description.

The arrow X indicates the direction in which the oscillations are propagating in the hollow wave-guides whilst an arrow Z indicates the direction of the electronic current in the discharge tube. The direction normal to the X- and Z- directions is indicated by an arrow Y.

According to the invention, the dimensions b of the tube, which is the transverse dimension in the Y-direction, has to satisfy a definite condition since it is necessary for the dimension 1) to be larger than half of the wavelength which the oscillations to be amplified exhibit when propagating in the free space. In fact, if I) would be given a value smaller than that which ensues from this condition there is no propagation of energy in the wave-guide. Consequently, the di- J at From this relation ensues first of all that xx only has significance so long as A is smaller than 217, and further that the value of M.- is always higher than that of A; under definite conditions when A is but slightly smaller than 213 this value can even be much higher than t. This circumstance is advantageously taken into account in proportioning the length Z of the electrode system.

Due to the reflection of the oscillations at the back of the wave-guide, a stationary wave will occur between the grid and the cathode in the longitudinal direction of the electrode system. When the wave-guide is closed at its end there is produced a stationary wave exhibiting at this place a node; if, however, the hollow wave-guide is not closed there is produced a stationary wave exhibiting at this place a loop. Figures 2 and 3 are cross-sectional views of the electrode system; the system has been given a length Z exactly equal to /gxx. Figure 2 illustrates the case wherein the wave-guides are closed and Figure 3 that wherein the wave-guides are not closed-hereinafter reference is only made to the effect of closure or non-closure of the lower wave-guide; in the upper wave-guide also stationary waves occur between the anode and the control grid, for which waves similar contemplations apply. The curve I in Figure 2 and the curve 8 in Figure 3 represent in each case the variation of the alternating voltage to be amplified so this is the voltage set up between the grid and the cathode as a function of the X-coordinate for example measured over the middle of the tube, hence at the place Y= [;b.

From the variation of the voltage represented in Figure 2 ensues that the electronic current is influenced by this voltage in the same sense throughout the length of the cathode. Consequently, all points of the cathode assist in the same manner, in phase, in the amplification.

' This is not the case, however, with the situation illustrated in Figure 3. In this case the electronic current on each side of point P located in the middle of the cathode is controlled by the voltage in anti-phase, so that the total amplification of the tube is reduced almost to nil. From this follows that, if it is desired to obtain as high an amplification as possible, the electrode system in the case of the non-closed wave-guide must preferably be given a length not greater than fl hx; in this case the cathode extends only from the end as far as point P, so that the whole electronic current of the tube is controlled in phase. In the case of a closed wave-guide it can immediately be deduced from the foregoing that the electrode system must preferably be given a length not greater than /2)\;;.

Consequently, the discharge tube described before has dimensions which need not be reduced with an increase in frequency of the oscillations to be amplified, since the transverse dimension D of the tube is bound to a definite minimum dimension and the dimension in the longitudinal direction may be given a value efficacious in practice by a correct choice of the relation A/Zb see the above-mentioned relation between M, A and Z). From the foregoing it follows that in spite of its comparatively large size the discharge tube according to the invention can amplify oscillations of very high frequency and, precisely owing to this large size more particularly owing to the large size of the electron-emitting surface can on principle give off or transmit any desired power.

In view of the fact that as a rule direct voltages of different values must be supplied to the various electrodes, these must be constructed so as to be relatively insulated. Apart from this insulation the sides of the hollow wave-guides that is the sides at the laces Y=O and Y=b may be closed while the e ectrodes at these places can be coupled capacitatively, if desired. The direct-current sources are omitted in the figure for simplicitys sake.

The supply and the derivation of the voltages in the circuit shown in Figure 1 was effected with the aid of a Lecher line. This may, of course, also be effected in a different manner, for example by means of hollow wave-guides, or with the aid of concentric Lecher systems. It is also not necessary for the voltages to be supplied and derived at opposite ends of the discharge tube; the points of supply and of derivation may also be provided at arbitrary angles relatively to each other.

One form of construction of the circuit shown in Figure 1, in which the electrode system of the triode has a cylindrical shape, is shown diagrammaticaly in Figure 4. The transverse dimension b of triode 2 is here determined by the average circumference of the tube, that is for example by the circumference of control grid 5.

Figure 5 shows the same triode. The voltage to be amplified and the amplified voltage are supplied to the triode and derived from it with the aid of concentric Lecher systems which gradually change into the hollow wave-guides. The coup ing between the two Lecher systems and the triode may be effected, for example, through condensers. These condensers as well as the direct-current sources are omitted in Figure 5. The dimension of the hollow wave-guides measured in the direction of the electronic current of the discharge tube is generally small relatively to the other dimensions of the wave guides. This dimension is mainly determined by the transit-times of the electrons in the tube.

In those cases wherein the longitudinal dimension of the electrode system of the discharge tube is larger than that which corresponds to the above-mentioned conditions, it is advantageous to make those parts of the electrode system inactive which detrimentally afiect the transmission or the production of oscillations, or it is possible to close the wave-guides by their surge resistances or by appropriate impedances free from losses.

The present invention also applies brakingfield circuits as Well as to circuits in which frequency-changing takes place; the discharge tubes that can be used in the circuit according to the invention are not limited to those of the triode type; diodes, tetrodes, pentodes, etc. can also be used.

What we claim is:

1. An electron discharge device adapted to generate or amplify oscillations of the Ho-type at a predetermined wavelength, said device comprising planar cathode, grid and anode electrodes of like rectangular shape successively mounted in spaced parallel relation, said electrodes constituting opposing surfaces of two waveguides of rectangular cross section, said grid electrode being common to both guides, the dimension of said two guides in the direction normal both to the direction of propagation in the guides and to the direction of electron fiow oetween the cathode and anode electrodes having a value greater than a half wavelength of said oscillations in free space.

2. An electron discharge device adapted to generate or amplify oscillations of the Hu-type at a predetermined wavelength, said device comprising cathode, grid and anode plane electrodes of like rectangular shape successively mounted in spaced parallel relation, and opposing wall means effectively connecting the longitudinal edges of said electrodes for high frequencies thereby to define a pair of open-ended hollow waveguides of rectangular cross section, said grid electrode being common to both guides whereby electrons from the cathode electrode in one guide passes through said grid electrode to reach the anode electrode in the other guide, the transverse dimension of said guides having a value exceeding a half wavelength of said oscillations when propagated in free space.

3. An electron discharge device as set forth in claim 2 wherein the longitudinal dimension of said guides has a value which is less than a quarter wavelength of said oscillations when propagated within said guides.

4. An electron discharge device adapted to generate or amplify oscillations of the Ho-type at a predetermined wavelength, said device comprising cathode, grid and anode plane electrodes of like rectangular shape successively mounted in spaced parallel relation, opposing Wall means effectively connecting the longitudinal edges of said electrodes for high frequencies, and opposing wall means efiectively connecting the transverse edges of said electrodes for high frequencies thereby to define a pair of enclosed hollow wave-guides of rectangular cross section, said grid electrode being common to both guides whereby electrons from the cathode electrode in one guide passes through said grid electrode to reach the anode electrode in the other guide, the transverse dimension of said guides having a value exceeding a half wavelength of said oscillations when propagated in free space, the longitudinal dimension of said guides having a value smaller than a half wavelength of said oscillations when propagated within said guides.

MAXIMILIAAN JULIUS OTTO STRUTT. ALDERT VAN DER ZIEL. KORNELIS SWIER KNOL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,122,538 Potter July 5, 1938 2,284,405 McArthur May 26, 1942 2,409,417 Bull Oct. 15, 1946 2,409,608 Anderson Oct. 22, 1946 2,425,748 Llewellyn Aug. 19, 1947 

